The tax-free treatment of the spinoffs Dow Chemical Co. and DuPont Co. plan after they merge is one of the main forces behind the deal and could save tens of billions of dollars, Reuters reported. “The whole structure of this is very, very tax efficient and one of the reasons we are doing it this way, so very beneficial from that standpoint to the shareholders,” DuPont CEO Ed Breen told analysts on Friday. “When I looked at every other strategic option to DuPont, there was nothing that came close to this.” Pfizer Inc. recently said it would use its $160 billion acquisition of Allergan PLC as a way to cut its taxes. It underscores the growing use of mergers and acquisitions as a way to slash corporate America’s tax bill.